[geos-devel] Re: Polygonizer bug ?

[strk]

FYI, as of r3078 the mis-port is fixed in GEOS.
Still interested in the result after self-noding.
Thanks !

--strk;

On Thu, Jul 01, 2010 at 10:59:12PM +0200, strk wrote:
> On Mon, Jun 21, 2010 at 09:13:16AM -0700, Martin Davis wrote:
> > strk,
> > 
> > The JTS Developer's Guide is a bit confusing.  The geometry given in the 
> > example is NOT the geometry depicted in the illustration. (This is  a 
> > doc bug - but I"m not sure if and when I can fix it).
> > 
> > When I run the geometry below in JTS I get:
> > 
> > Polygons:
> > GEOMETRYCOLLECTION (
> >  POLYGON ((189 98, 83 187, 185 221, 325 168, 189 98)),
> >  POLYGON ((185 221, 88 275, 180 316, 292 281, 185 221)))
> > 
> > Dangles:
> > MULTILINESTRING ((185 221, 100 100),
> >  (0 0, 10 10))
> > 
> > I believe this is the expected result.
> 
> Uhm, that's w/out self-noding, right ?
> 
> --strk;
> 
> 
> > 
> > Hope that helps
> > 
> > Martin
> > 
> > strk wrote:
> > >Martin, I'm adding a testcase for the Polygonizer using example from :
> > >"JTS Developer's Guide, Chapter 6 - Polygonization"
> > >
> > >Here's the input, represented as a collection:
> > >
> > >GEOMETRYCOLLECTION(
> > >            LINESTRING(0 0, 10 10),
> > >            LINESTRING(185 221, 100 100),
> > >            LINESTRING(185 221, 88 275, 180 316),
> > >            LINESTRING(185 221, 292 281, 180 316),
> > >            LINESTRING(189 98, 83 187, 185 221),
> > >            LINESTRING(189 98, 325 168, 185 221))
> > >)
> > >
> > >When passing it into the Polygonizer class I get
> > >2 rings, no cut or invalid edges and 3 dangles.                            
> > >Also notable is that of the 3 dangles, 2 are identical
> > >and specificall are the isolated edge (first geometry
> > >in the collection).
> > >
> > >The example in the guide suggests the rings should
> > >be 3 instead, and that there should be one cut
> > >edge (represented in blue) and 2 dangles
> > >the red ones.
> > >
> > >Does it sound as a bug in GEOS or does JTS give the
> > >same results ?
> > >
> > >Note that forcing proper noding using the union trick
> > >does give the 3 expected rings, but still lacks the
> > >cut edge and duplicates the dangle.
> > >
> > >Thanks in advance.
> > >
> > >--strk;
> > >
> > >  ()   Free GIS & Flash consultant/developer
> > >  /\   http://strk.keybit.net/services.html
> > >  
> > 
> > -- 
> > Martin Davis
> > Senior Technical Architect
> > Refractions Research, Inc.
> > (250) 383-3022
> 
> -- 
> 
>   ()   Free GIS & Flash consultant/developer
>   /\   http://strk.keybit.net/services.html
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-- 

  ()   Free GIS & Flash consultant/developer
  /\   http://strk.keybit.net/services.html